(Changes to reflect launch of robotaxi trial)

By Chris Kirkham, Norihiko Shirouzu, Rachael Levy and

Abhirup Roy

June 22 (Reuters) - Tesla tiptoed into its

long-awaited robotaxi service in Austin, Texas on Sunday with

about 10 of its Model Y SUVs that will operate within strict

limits.

The rides were being offered on Sunday for a flat fee of

$4.20, CEO Elon Musk said in an X post, and social media

influencers were seen booking and taking rides in the robotaxis

in several Austin locations, according to videos reposted by

Musk.

Musk has said the company is being "super paranoid" about

safety and that humans will remotely monitor the fleet, which

also have safety monitors in front passenger seats.

Remote access and control - known in the industry as

"teleoperation" - is used in varying degrees by the handful of

robotaxi startups operating around the globe. The technology has

clear advantages and important limitations.

Here are some details of how it works:

WHAT IS TELEOPERATION?

Teleoperation is the control of machines by humans in a

different location, usually over a wireless network.

It is used to train robots to operate autonomously, monitor

their autonomous activity, and take over when required.

HOW DO ROBOTAXI OPERATORS USE TELEOPERATION?

The global robotaxi industry is still in test mode, as

companies deploy the vehicles in limited geographic areas and

continually adjust the artificial intelligence software that

controls them. Teleoperation is often used to intervene when a

vehicle is unsure of what to do.

Alphabet's Waymo, for example, has a team of human

"fleet response" agents who respond to questions from the Waymo

Driver - its bot.

"Much like phone-a-friend, when the Waymo vehicle encounters

a particular situation on the road, the autonomous driver can

reach out to a human fleet response agent for additional

information," Waymo said in a blog post last year.

Former Waymo CEO John Krafcik told Reuters, "the cars aren't

being actively monitored," adding that the software is "the

ultimate decision-maker."

A Waymo video shows a car asking a remote operator whether a

street with emergency response vehicles is open to traffic. When

the human says yes, the vehicle proceeds.

In contrast, other companies, such as Baidu's Apollo Go in

China, have used fully remote backup drivers who can step in to

virtually drive the vehicles. Baidu declined to comment.

WHAT ARE THE LIMITATIONS?

Driving vehicles remotely on public roads has a major

potential problem: it relies on cellular data connections that

can drop or operate with a lag, disconnecting the vehicle from

the remote driver in dangerous situations.

Philip Koopman, a Carnegie Mellon University engineering

professor and autonomous-vehicle safety expert, said that

approach could work for a small test deployment of 10 vehicles,

such as Tesla's initial effort in Austin, but he called

teleoperation "inherently unreliable technology."

"Eventually you will lose connection at exactly the worst

time," he said. "If they've done their homework, this won't ever

happen for 10 cars. With a million cars, it's going to happen

every day."

Former Waymo CEO Krafcik agreed, adding that the time delay

in cell signal makes remote driving "very risky."

On the other hand, relying on the vehicle to reach out for

help and allowing the vehicle to be the decision-maker are risky

as well, Koopman said, as it does not guarantee the vehicle will

make the right decision.

Waymo declined to comment on the limitations of its

approach.

Koopman also noted there are limits to how many vehicles one

person can safely monitor.

A group of Democratic Texas lawmakers had asked Tesla on

Wednesday to delay its robotaxi launch until September, when a

new autonomous-driving law is scheduled to take effect. The

Austin-area lawmakers said in a letter that delaying the launch

"is in the best interest of both public safety and building

public trust in Tesla's operations."

WHAT IS TESLA'S APPROACH?

Musk for years has promised, without delivering, that its

Full Self-Driving (Supervised) advanced driver

assistance software would graduate to completely self-driving

and control robotaxis. This year, he said Tesla would roll out a

paid service in Austin underpinned by an "unsupervised" version

of the software.

"Teslas will be in the wild, with no one in them, in June,

in Austin," Musk told analysts and investors in January. In May,

he told CNBC that the robotaxi would only operate in parts of

Austin that are safe for it, would avoid difficult

intersections, and would use humans to monitor the vehicles.

What those teleoperators are doing is not clear.

For years inside Tesla, company executives have expected to

use teleoperators who could take over in case of trouble, said

one person familiar with the matter. For instance, if a robotaxi

were stuck in a crowded pedestrian area and confused about what

to do next, a human teleoperator could take over and guide it,

the source said.

Tesla advertised for teleoperation positions, saying the

company needs the ability to "access and control" autonomous

vehicles and humanoid robots remotely. Such employees can

"remotely perform complex and intricate tasks," it said in the

advertisements.

Tesla did not respond to a request for comment.

"We are being super paranoid about safety," Musk said in a

post ahead of the launch.